The bone marrow-derived dendritic cells (DL/LC) are antigen-presenting accessory cells functioning as part of the immune system. In addition, DC/LC in epithelial tissues may have the capacity to be involved in cellular interactions which may have regulatory functions. Such properties can also be noted when LC/DC interact with cancer cells in tumors. The present review summarizes reports which suggest that the outcome of a primary tumor in patients depends on the presence or absence of DC/LC in the tumor. The evidence showing that the presence of DC/LC in primary tumors indicates that a good prognosis may be reached are presented and discussed. Based on these observations and the ability of immunomodulators to enhance the activity of DC/LC and the ability of these cells to enter into tumors, it is suggested that the molecular basis of DC/LC activity against primary tumors cells should be investigated. It is possible that activation of DC/LC, thereby enhancing their ability to enter primary tumors, and the abrogation of the ability of DC/LC-resistant tumors to destroy or prevent DC/LC from entering the tumor, could be developed as an effective anti-cancer approach.